Corrugated paperboard is widely used as a material for fabricating containers and for other packaging applications. Corrugated paperboard is strong, lightweight, relatively inexpensive, and may be recycled. Conventional corrugated paperboard is constructed of two opposing liners and an intervening fluted sheet secured together using an adhesive. In some applications, it may be desirable to apply a coating to one or more components of the corrugated paperboard, such as to resist moisture penetration, for example, as when used to package food products. A coating, such as a paraffin wax or tallow wax, may be heated to a liquid state and applied to a continuous paper sheet component of the corrugated paperboard.
U.S. Pat. No. 4,384,544 discloses a wax coating apparatus comprising a first pair of cylindrical rollers, each having a smooth surface which is exposed to and wetted by the liquid to be applied, and being rotatably mounted about substantially parallel axes and spaced apart to permit intimate tangential contact therebetween with both sides of the sheet material to be coated. A second pair of cylindrical rollers located a distance from the first pair are similarly mounted and positioned to make contact with the sheet material in like manner. A pair of cylindrical engraved rolls, each having an array of quadrangular cells formed along the surfaces thereof, are respectively positioned between each of the first and second pairs of rollers, and are rotatably mounted on movable axes so that the engraved rolls urge against one or both of the roller pairs during rotation.
Profero Systems, Inc. of Dallas, N.C., the assignee of the present application, also offers and sells its Versa Waxer model to apply wax to a continuous paper sheet for corrugated paperboard manufacturing. The Versa Waxer includes a frame, an entry guide roll and an exit guide roll both carried by the frame and along a path of travel of the paper. A single hot wax applicator is carried by the frame between the entry and exit guide rolls. The single hot wax applicator includes a press roll, an engraved applicator roll below and opposite the press roll so that the continuous paper sheet is therebetween, and with the engraved applicator roll extending into a hot wax reservoir to pick up hot wax. A doctor blade is adjacent the engraved applicator roll to control a thickness of hot wax. K&R Corrugated Equipment, Inc. of San Jose, Calif. also offers a wax applicator including a single wax applicator including a single engraved applicator roll.
Prior to the use of the engraved applicator roll, wax was typically applied with other types of applicators at a rate of about 7-11 lbs./1000 sq.ft. This was because the application rate could not be very accurately controlled. The higher usage of wax for the higher rate of coating, unfortunately, resulted in higher expenses. An applicator using a single engraved roll, such as the Profero Systems' Versa Waxer, represents a significant improvement in wax application, because the application can be more accurately controlled, and, thus, less wax used.
Unfortunately, corrugated paperboard plants may now desire to run different paper components with different wax application rates. Using the single engraved roll applicator, a typical approach is to change out the engraved roll if a different application rate is desired. And the time for the roll change, assuming another engraved roll is readily available, may take about 8-10 hours of time. Space for a wax coating apparatus is also very constrained in a typical corrugated paperboard plant.